A magnetoresistive element (MR element) is an element which detects magnetic field changes on the basis of a magnetoresistive effect that produces changes in electrical resistance as a magnetic field varies. For a high detection sensitivity of such a magnetoresistive element, its application to reproduce heads for magnetic recording media, such as a hard disc, has been expected. However, technology has shown the continuous growth of recording density in hard discs. For application of the magnetoresistive element to reproduce heads for further improved high density recording media, it will likely need to exhibit a still higher sensitivity. If the magnetoresistive element is to increase in sensitivity, its MR ratio must be raised. In the attempt to obtain a magnetoresistive element exhibiting a high MR ratio, a giant magnetoresistive element (GMR element) has been investigated which utilizes a magnetoresistive film having a multilayer structure consisting of a ferromagnetic layer and a nonmagnetic conductive layer. As a result, a variety of GMR element designs has been proposed heretofore. Known GMR element designs include, for example, a coercivity differential type GMR element of a structure having a nonmagnetic conductive layer interposed between a pair of ferromagnetic layers having different coercive forces; a spin-valve type GMR element having a nonmagnetic conductive layer interposed between a pair of ferromagnetic layers one of which pins an antiferromagnetic layer thereon; and an artificial lattice type GMR element consisting of ferromagnetic layers and nonmagnetic conductive layers repeatedly stacked in plural periodic sequences.
However, in order to achieve a further improvement in recording density, GMR elements need to have further higher MR ratios. The development of GMR elements which permit the use of a narrow track width has been also demanded.
An object of the present invention is directed toward meeting the needs as sought heretofore and resides in its provision of a novel structure of a magnetoresistive element which can exhibit a higher MR ratio than conventional.